This is a study to determine the effects of methadone during pregnancy in the immediate newborn period and the first 3 years of life. The effects to be studied include somatic, neurological and behavioral and social development in the newborn and child. In addition, pharmacokinetic studies are performed in the mother during pregnancy and in the newborn to try to relate these to the immediate neonatal effects and perhaps the later outcome of the young child. We enroll our patients from the Perinatal High Risk Clinic and follow the mothers closely with urine and blood collections for methadone and metabolite excretions. At delivery, we analyze the methadone levels again in the mother, umbilical artery and venous bloods, and in the newborn at designated times to determine the rate of elimination and methadone excretion. In addition, we do daily evaluations of the newborn using withdrawal scoring system, the Brazelton Behavioral Assessment Exam, as well as habituation and mother-infant interaction studies. The infants are followed every 2 months in the follow-up clinic where they are again evaluated somatically, behaviorally and socially for the first 3 years of life. In order to ensure good follow-up we also provide primary medical care, well-baby care and immunizations and have a social worker available to give social and economic assistance when necessary. We hope by examining these multiple variables we will be able to determine whether methadone is beneficial or deleterious to children during the first 3 years of life whose mothers were maintained on the drug.